1. Field
One or more aspects of embodiments of the present disclosure relate to a material for an organic electroluminescent device, an organic electroluminescent device using the same, a method of preparing triarylamine derivatives, a hole transport material for an organic electroluminescent device having high emission efficiency and long life, an organic electroluminescent device using the same, and/or a preparation method of the material for an organic electroluminescent device.
2. Description of the Related Art
Organic electroluminescent (EL) displays are currently being actively developed. Unlike liquid crystal displays, etc., organic EL displays are so-called self-luminescent displays that function by recombining holes and electrons from an anode and a cathode in an emission layer to generate excitons for emitting light energy. Light is emitted from a luminescent organic compound in the emission layer.
An example organic EL device includes an anode, a hole transport layer on the anode, an emission layer on the hole transport layer, an electron transport layer on the emission layer, and a cathode on the electron transport layer. Holes injected from the anode move via the hole transport layer to the emission layer. Electrons injected from the cathode move via the electron transport layer to the emission layer. When the holes and electrons injected into the emission layer are recombined, excitons are generated in the emission layer. The organic EL device emits light using energy generated by the radiative decay of the excitons. Configurations of the organic EL device are not limited to the above example, and may be diversely modified.
When organic EL devices are used in display apparatuses, the organic EL devices should exhibit high emission efficiencies and long lifetimes. However, driving voltages are high and emission efficiencies are insufficient in many organic EL devices, for example, those in the blue emission region. Methods of increasing the normalization, stabilization, and durability of the hole transport layer have been examined as strategies for increasing the efficiencies and lifetimes of organic EL devices.
Many aromatic amine compounds are available as hole transport materials for use in a hole transport layer. For example, an amine derivative substituted with a heteroaryl ring has been suggested as a useful material for increasing the emission efficiency of an organic EL device in the blue emission region. However, issues related to resolving the emission efficiency of the device remain, and it is difficult to say that an organic EL device using the material has a sufficient emission efficiency. For example, the emission efficiencies of organic EL devices are low in the blue emission region relative to the red and green emission regions, and an increase of emission efficiency in the blue emission region is desirable. An aniline derivative having aryl groups at positions 2 and 6 has been suggested as a material for increasing the emission efficiency of an organic EL device; however, a device using the material was not considered to have sufficient emission efficiency. An aniline derivative having substituents at positions 2 and 6 has been disclosed as a luminescent material but was considered to be inappropriate or unsuitable as a hole transport material, because the amine site is a ring shape (e.g., contained within a cyclic moiety) and the compound includes an electron withdrawing group. Accordingly, further developments on material for an organic EL device having an even higher efficiency are needed.